Drill bits for subterranean drilling, such as drilling for hydrocarbon deposits in the form of oil and gas, conventionally include internal passages for delivering a drilling fluid, or “mud,” to locations proximate a cutting structure carried by the bit. In fixed cutter drill bits, or so-called “drag” bits, the internal passages terminate proximate the bit face at locations of nozzles received in the bit body for controlling the flow of drilling mud used to cool and clean the cutting structures (conventionally polycrystalline diamond compact (PDC) or other abrasive cutting elements). Some drill bits, termed “matrix” bits, are fabricated using particulate tungsten carbide infiltrated with a molten metal alloy, commonly copper-based. Other drill bits, termed “cemented” bits, are fabricated by sintering particulate tungsten carbide and a metal or metal alloy, commonly cobalt- or nickel-based. Still other drill bits comprise steel bodies machined from blanks, billets or castings. Steel body drill bits are susceptible to erosion from high pressure, high flow rate drilling fluids, on both the face of the bit and the junk slots as well as internally. As a consequence, on the bit face and in other high-erosion areas, hardfacing is conventionally applied. Within the bit, erosion-resistant components such as nozzles and inlet tubes fabricated from tungsten carbide or other erosion-resistant materials are employed to protect the steel of the bit body. “Matrix” bits and “cemented” bits are less susceptible to this erosion, but still require nozzles for creating desired fluid flow parameters. The nozzles, regardless of the material used in the bit body, allow fluid flow to be specified or selected to obtain various flow rates and patterns.
As shown in FIG. 7 of the drawings, a conventional steel body drill bit 500 for use in subterranean drilling may include a plurality of nozzle assemblies, exemplified by illustrated nozzle assembly 501. While many conventional drill bits use a single piece nozzle, the nozzle assembly 501 is a two piece replaceable nozzle assembly, the first piece being a tubular tungsten carbide inlet tube 502 that fits into an internal fluid port or passage 504 machined in the body of the drill bit 500, and is seated upon an annular shoulder 505 of port 504. The second piece is a tungsten carbide nozzle 503 that may have a restricted bore 513 that is secured within port 504 of the drill bit 500 by threads which engage mating threads 506 on the wall of port 504. The inlet tube 502 is retained in port 504 by abutment between the annular shoulder 505 and the end of the nozzle 503. The inlet tube 502 and the nozzle 503 are used to provide protection to the material of the steel body drill bit 500 through which port 504 extends against erosive drilling fluid effects by providing a hard, abrasion- and erosion-resistant pathway from an inlet fluid chamber or center plenum 507 within the bit body to a nozzle exit 508 located proximate to an exterior surface of the bit body. The inlet tube 502 and nozzle 503 are replaceable should the drilling fluid erode or wear the parts within internal passage 509 extending through these components, or when a nozzle 503 having a different orifice size is desired; however, it is intended that the inlet tube 502 and nozzle 503 will protect the material of the bit body surrounding the internal fluid port 504 from all erosion. Further, the outer surface or wall of the nozzle 503 is in sealing contact with a compressed O-ring 514 disposed in an annular groove formed in the wall of port 504 to provide a fluid seal between the steel body drill bit 500 and the nozzle 503.
In order to retain the nozzle 503 within the port 504 of the steel body drill bit 500, the threads 506 must necessarily be of high quality and machined to desired tolerances. Obtaining the desired machined threads 506 is readily obtainable in a drill bit made from steel material. However, obtaining the desired quality threads with the required tolerances in a bit composed of a material, such as a “cemented” carbide, for example, requires forming or machining the threads prior to final sintering of the bit body material. The volumetric change that occurs during the sintering process may ultimately lead to distortion or lower quality of threads, which may require further post-sintering processing which increase the cost of manufacturing.
Accordingly, it is desirable to provide for threaded attachment of a nozzle in which the precision tolerances may be obtained by a threaded attainment regardless of the material selected for the body of the drill bit. Also of advantage would be to provide a threaded attachment that is achievable after the bit body is substantially manufactured, particularly for bit bodies manufactured by sintering or infiltration processes. It is also desirable to provide for a threaded nozzle attachment that allows for standardized nozzles to be used therewith. A further advantage would be to provide a nozzle assembly of a design that may be suitable for either replacement and retrofit applications for existing drill bits, as well as in the manufacture of new drill bits, without requiring complicated and costing manufacturing or remanufacturing techniques.